There have been developed a multitude of filters and filtration systems to remove contaminants from contaminated fluids, particularly contaminated water. While many of the filters function effectively for purifying contaminated water, the filters eventually become clogged with the removed contaminants and must be replaced periodically to ensure satisfactory filtration. Alternatively, the filters can be back-flushed to regenerate the filters to extend the useful life of the filters. The regeneration of the filters, however, is sometimes as troublesome as replacing the filter and may involve substantial quantities of wash solutions. Some of the filtration systems that have been previously devised are described below.
U.S. Pat. No. 1,993,345 discloses a process for reviving an adsorbent bed such as of activated carbon, activated alumina, and silica gel by employing superheated steam for the heating of the adsorbent and the driving out of impurities and then very suddenly chilling the adsorbent throughout the bed by totally or partially flooding the adsorbent with liquid carbon dioxide.
U.S. Pat. No. 4,075,281 pertains to the purification of carbonate process solutions which comprises passing the carbonate process solution through a bed of activated carbon to remove organic contaminants until the adsorbent capacity of the bed is reduced and then regenerating the adsorbent bed by passing an aqueous solution at elevated temperature through the adsorbent bed to remove the adsorbed organic contaminants. The temperature of the hot aqueous wash is about 50.degree.-95.degree. C., preferably 60.degree.-90.degree. C. Multiple aqueous washes may be employed, with such aqueous washes employing previously employed aqueous washes. For example, the adsorbent bed may be purified by an initial wash with the contaminated solution, followed by a slightly contaminated solution wash, and lastly with a substantially purified aqueous solution wash. The wash solutions can then be reused in the next washing cycle, e.g., the slightly contaminated wash solution may be reused as a contaminated solution wash in the next adsorbent bed purification cycle.
U.S. Pat. No. 4,081,365 discloses a process for use in water purification, particularly in sewage treatment, in which the sewage is subjected to a primary biological treatment and a secondary settling treatment, with the primary-secondary effluent being subjected to a tertiary treatment by passage through a mixed filtration and adsorption bed containing activated carbon. The mixed bed is periodically regenerated by a partial wet-gas oxygenation cycle, utilizing a reflux operation in which the products of regeneration are returned to the primary treatment and in which the final effluent is conceivably, with the addition of chlorination, potable water. The disclosed system contemplates a storage system for renovating water which receives effluent from the tertiary treatment, can be heated, and then is used in connection with the reactivation or regeneration of the material of the tertiary treatment system.
U.S. Pat. No. 4,161,446 describes a process for the treatment of ground water to render it potable by prefiltration, degassing, passing through thermal ion exchange desalination resins, and reverse osmosis treatment. After prefiltration and degassing, most of the water is directed to the thermal ion exchange resin, while a portion is heated to about 60.degree.-98.degree. C. and directed to a thermal storage unit. After the thermal ion exchange resin becomes contaminated and relatively ineffective, the water flow through the thermal ion exchange resin is redirected to the thermal storage unit, and the thermal storage unit water is used to back-flush the thermal ion exchange resin and thereby regenerate it. The portion of the regenerate wash which is heavily contaminated with undesirable salts may be withdrawn and passed to waste disposal, while the remaining portion which is relatively free of undesirable contaminants may be recycled, passed through a heat exchanger (with the extracted heat being passed to the raw ground water inflow to the prefilters), subjected to a heat pump system (in which the extracted residual heat is passed to the thermal storage unit), and treated in a reverse osmosis system to provide potable water which is commingled with the potable water provided by the thermal ion exchange resin.
U.S. Pat. No. 4,725,361 discloses a process for the removal of trihalocarbons from water. Water contaminated with a trihalocarbon is passed through a first or second bed containing particles of an activated composite adsorbent comprising alumina and zeolite. The trihalocarbon is adsorbed onto the particles, thereby reducing the trihalocarbon concentration in the water. The adsorbed trihalocarbon is reacted with air or steam at an elevated temperature in order to regenerate the adsorbent particles for reuse. Gaseous hydrochloric acid produced in the reaction with air or steam may be adsorbed in a third bed containing adsorbent agglomerates.
While the prior art discloses a variety of ways of purifying fluids, particularly water, and of regenerating the filters used in the purification processes, there remains a need for a simple and economical purification and regeneration process which results in a minimum of waste fluid.